agronomy Article Field Screening of Wheat Advanced Lines for Salinity Tolerance Ehab S. A. Moustafa 1 , Mohamed M. A. Ali 2 , Mohamed M. Kamara 3 , Mohamed F. Awad 4 , Abdallah A. Hassanin 5 and Elsayed Mansour 2, *   Citation: Moustafa, E.S.A.; Ali, M.M.A.; Kamara, M.M.; Awad, M.F.; Hassanin, A.A.; Mansour, E. Field Screening of Wheat Advanced Lines for Salinity Tolerance. Agronomy 2021, 11, 281. https://doi.org/10.3390/ agronomy11020281 Academic Editor: Ajay Kumar and Santosh Kumar Received: 5 January 2021 Accepted: 1 February 2021 Published: 3 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Desert Research Center, Genetic Resources Department, Cairo 11753, Egypt; ehab.soudi@yahoo.com 2 Department of Crop Science, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt; abd_lhamed@yahoo.com 3 Department of Agronomy, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt; mohamed.kamara@agr.kfs.edu.eg 4 Department of Biology, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia; m.fadl@tu.edu.sa 5 Genetics Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt; dr.abdallah4@gmail.com * Correspondence: sayed_mansour_84@yahoo.es Abstract: Salinity in soil or irrigation water requires developing genetically salt-tolerant genotypes, especially in arid regions. Developing salt-tolerant and high-yielding wheat genotypes has become more urgent in particular with continuing global population growth and abrupt climate changes. The current study aimed at investigating the genetic variability of new breeding lines in three advanced generations F6–F8 under salinity stress. The evaluated advanced lines were derived through accurate pedigree selection under actual saline field conditions (7.74 dS/m) and using saline water in irrigation (8.35 dS/m). Ninety-four F6 lines were evaluated in 2017–2018 and reduced by selection to thirty- seven F7 lines in 2018–2019 and afterward to thirty-four F8 lines in 2019–2020 based on grain yield and related traits compared with adopted check cultivars. Significant genetic variability was detected for all evaluated agronomic traits across generations in the salt-stressed field. The elite F8 breeding lines displayed higher performance than the adopted check cultivars. These lines were classified based on yield index into four groups using hierarchical clustering ranging from highly salt-tolerant to slightly salt-tolerant genotypes, which efficiently enhance the narrow genetic pool of salt-tolerance. The detected response to selection and high to intermediate broad-sense heritability for measured traits displayed their potentiality to be utilized through advanced generations under salinity stress for identifying salt-tolerant breeding lines. Keywords: yield-related traits; genotypic and phenotypic coefficient of variation; broad-sense heritability; response to selection; genetic gain; cluster analysis; principal component analysis 1. Introduction Wheat (Triticum aestivum L.) is a widespread staple food crop worldwide. It is a major source of energy and starch, as well as provides considerable amounts of dietary fiber, protein, and vitamins for human nutrition [1,2]. The total production amount of wheat in 2018 was 734.1 million tons, harvested from 214.3 million hectares [3]. Current and projected future population growth requires improving wheat production in response to worsening challenges due to climate change [4–6]. Salinity is one of the harsh environmental factors that devastatingly impact global wheat production [7,8]. Large areas of cultivated land around the world are salt-affected, particularly in arid regions due to low precipitation, high evaporation, poor drainage, poor irrigation practices, using saline water in irrigation, or rising water tables [7,9]. Under salinity conditions, wheat plants suffer from high osmotic stress, difficulties in nutrient uptake, and ion toxicity, which is reflected in reducing cell turgor and limiting growth and productivity [8,10]. Agronomy 2021, 11, 281. https://doi.org/10.3390/agronomy11020281 https://www.mdpi.com/journal/agronomy